Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W = map(int,input().split())
l = [str(input()) for _ in range(H)]
white_count = 0
for s in l:
  white_count += s.count('.')
sy = 0
sx = 0
gy = H-1
gx = W-1
visited = [[-1]*W for _ in range(H)]
visited[sy][sx] = 0
Q = deque([[sy,sx]])
while Q:
  y,x = Q.popleft()
  if [y,x] == [gy,gx]:
    print(white_count - visited[y][x] - 1)
    exit()
  for i,j in [(1,0),(0,1),(-1,0),(0,-1)]:
    if 0 <= x+j < W and 0 <= y+i < H and visited[y+i][x+j] == -1 and l[y+i][x+j] == '.':
      visited[y+i][x+j] = visited[y][x]+1
      Q.append([y+i,x+j])
    else:
      continue
print(-1)